Re: [PATCH net v2] net: ipv6: fix TCP GSO segmentation with NAT

[kernel test robot <lkp@intel.com>]

Hi Felix,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Felix-Fietkau/net-ipv6-fix-TCP-GSO-segmentation-with-NAT/20250310-192256
base:   net/main
patch link:    https://lore.kernel.org/r/20250310112121.73654-1-nbd%40nbd.name
patch subject: [PATCH net v2] net: ipv6: fix TCP GSO segmentation with NAT
config: s390-randconfig-001-20250312 (https://download.01.org/0day-ci/archive/20250312/202503120224.LbO66Ztw-lkp@intel.com/config)
compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250312/202503120224.LbO66Ztw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202503120224.LbO66Ztw-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/ipv6/tcpv6_offload.c:104:30: warning: variable 'th' is uninitialized when used here [-Wuninitialized]
                   inet_proto_csum_replace16(&th->check, seg,
                                              ^~
   net/ipv6/tcpv6_offload.c:101:19: note: initialize the variable 'th' to silence this warning
           struct tcphdr *th;
                            ^
                             = NULL
   1 warning generated.


vim +/th +104 net/ipv6/tcpv6_offload.c

    95	
    96	static void __tcpv6_gso_segment_csum(struct sk_buff *seg,
    97					     struct in6_addr *oldip,
    98					     const struct in6_addr *newip,
    99					     __be16 *oldport, __be16 newport)
   100	{
   101		struct tcphdr *th;
   102	
   103		if (!ipv6_addr_equal(oldip, newip)) {
 > 104			inet_proto_csum_replace16(&th->check, seg,
   105						  oldip->s6_addr32,
   106						  newip->s6_addr32,
   107						  true);
   108			*oldip = *newip;
   109		}
   110	
   111		if (*oldport == newport)
   112			return;
   113	
   114		th = tcp_hdr(seg);
   115		inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
   116		*oldport = newport;
   117	}
   118	

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